1. Field of the Invention
The present invention relates to a scroll compressor, and particularly, to an apparatus for preventing overheating of a scroll compressor by which a high temperature portion of a compressor is prevented from being overheated above a designated temperature while driving and a construction thereof can be made more simple.
2. Description of the Background Art
In general, a refrigeration cycle system, as shown in FIG. 1, includes a compressor 1 for compressing a refrigerant, a condenser 2 for discharging heat to the exterior by condensing the refrigerant compressed in the compressor 1, an expansion valve 3 for lowering a pressure of the refrigerant condensed in the condenser 2, and an evaporator 4 for absorbing external heat by evaporating the refrigerant which has been passed through the expansion valve 3.
The compressor 1, the condenser 2, the expansion valve 3 and the evaporator 4 are connected all together by connection pipes 5 to form one cycle (a closed system).
The refrigeration cycle system is operated as follows.
First, when power is applied to the refrigeration cycle system, the compressor 1 begins its operation, and accordingly the refrigerant is compressed in the compressor 1 to be in a state of high temperature and high pressure and then discharged. The refrigerant in a gaseous state of high temperature and high pressure which has been discharged out of the compressor 1 then flows into the condenser 2, and is condensed as it discharges heat to the exterior while it flows through the condenser 2. As a result, the refrigerant is condensed into a fluid form. The refrigerant in the fluid state having passed through the condenser 2 goes through the expansion valve 3 and thus its pressure is lowered. The condensed refrigerant in the low pressure state flows into the evaporator 4, and then is evaporated into a gaseous state, as the refrigerant in the evaporator 4 absorbs external heat. The gaseous refrigerant at high temperature and high pressure having passed through the evaporator 4 flows into the compressor 1 again.
By repeating those procedures continuously, heat is discharged from condenser 2 to the outside, and the temperature is lowered in the evaporator 4.
Such refrigeration cycle system is typically mounted in an air-conditioner, a refrigerator, a showcase cooler and the like. The air-conditioner selectively transfers the heat generated in the condenser 2 to the exterior and extracts heat from an indoor area into the evaporator 4, and maintains a comfortable indoor state.
The compressor 1 constructing the refrigeration cycle system converts electrical energy into kinetic energy and compresses the refrigerant by the kinetic energy. As the compressor 1 is one of main components for the refrigeration cycle system, there are various types of compressors such as a rotary compressor, a scroll compressor, a reciprocal compressor, and the like.
The scroll compressor and the rotary compressor are generally used in the air-conditioner.
Scroll compressors are classified into a high pressure type and a low pressure type according to the state of pressure in a casing. In the high pressure type scroll compressor, the refrigerant directly flows in a gap between a fixed scroll and an orbiting scroll, and the refrigerant at high temperature and high pressure compressed between the fixed scroll and the orbiting scroll is discharged toward the condenser via an inside of the casing and a discharge pipe. As a result, the inside of the casing is always maintained in a state of high temperature and high pressure while the compressor operates.
In the low pressure scroll compressor, the refrigerant flows into the casing and is sucked into the gap between the fixed scroll and the orbiting scroll. The refrigerant at high temperature and high pressure compressed between the fixed scroll and the orbiting scroll is discharged toward the condenser via a high temperature and high pressure portion mounted on one side of the casing and the discharge pipe. As a result, the inside of the casing is always maintained in a state of low pressure while the compressor operates.
In designing the compressor, on the other hand, a high pressure portion of the compressor is designed to maintain a temperature within a range of a designated value in a state of a normal operation of the refrigeration cycle system. The temperature of the high pressure portion of the compressor is one of main design considerations. Accordingly, maintaining the high pressure portion of the compressor to be within the designated temperature range while operating has influences upon the capability, efficiency and reliability of the compressor, and also upon the capability and efficiency of the refrigeration cycle system having the compressor therein.
Therefore, the compressor is designed to have the high pressure portion operate within the designated temperature range.
However, an air-conditioner having the compressor therein is used in various different circumstances. Accordingly, when components of the air-conditioner are not allowed to properly perform their functions, the temperature of the high pressure portion of the compressor may be maintained at over the designated temperature whereby a life span of the compressor may disadvantageously be shortened, and breakdown thereof may be caused.
In order to solve such problem, when the temperature of the high pressure portion of the compressor is sensed and it is determined to be over the range of the designated temperature, fluid refrigerant is supplied toward the high pressure portion of the compressor to cool the high pressure portion of the compressor. As a result, the high pressure portion of the compressor is maintained within the range of the designated temperature.
However, for this method, a temperature sensor for sensing the temperature and a circuit for controlling a valve which controls injection of the fluid refrigerant are needed. As a result, a construction of the compressor may become complicated and the manufacturing cost thereof may be highly increased.